1. Field of Invention
This invention relates generally to personal protective equipment worn to prevent injuries, more specifically, to safety devices worn to help prevent lower back injuries that can be caused by lifting and bending activities.
2. Description of the Related Art
Lower back injuries remain the most prevalent and costly work-related musculoskeletal disorder facing industry today, both in the United States and in other Western industrialized countries. According to the National Institute for Occupational Safety and Health (NIOSH), back injuries account for nearly 20% of all workplace injuries at a cost of between 20 and 50 billion dollars annually.
Forward bending is perhaps the most significant risk factor for back injury. When individuals bend over using the lower back as a fulcrum to manually lift or lower objects (forward bending), the upper body is supported by the lower back. As the upper body moves from an upright position towards a bent position (approximately 90 degrees), the forces required by the lower back muscles to support the upper body increase dramatically due to the increased moment arm. During forward bending, the ligaments along the back portion of the spine are in an end-range stretch. They are stretched to their limit, making them vulnerable to being torn, especially if lifting something heavy. Perhaps most significantly during forward bending, the muscles in the lower back are fully stretched. When bending forward more than half way, the deep protective muscles of the lower back actually stop working! There is very little muscle protection to the lower back tissues in a position of full forward bending. All these loads are being placed on the discs, ligaments, and joints with very little muscle protection, and all of these stresses are magnified by the amount of time spent in forward bending.
There has been very little success in the search for ways to reduce the occurrence of back injuries related to lifting and bending, however, experts in this field still tend to agree that bending and lifting with proper technique (i.e. squat lifting with a straight back and bent knees) can help reduce the occurrence of lower back injuries. When you bend at the knees while you lift, you keep your back in alignment and let the stronger muscles in your thighs do the actual lifting. Many organizations have, or are developing programs, to protect against back injuries and teach proper lifting methods to their employees. Unfortunately, studies indicate that company educational programs do little to reduce the incidence of back pain. One reason there has been a lack of worker compliance with proper lifting technique, or squat lifting, may be because bending the knees lowers the torso which requires more energy than forward bending. Even workers who have been educated on proper lifting techniques may opt to bend or lift with improper form when fatigued.
Back belts are a type of safety device that have been very popular and are widely used. These belts typically wrap circumferentially around the lumbar region of the body, and are tightened to provide support to the lower back and abdomen. Many studies have been done in an attempt to determine if back belts help prevent injury, and despite their popularity, the scientific evidence tends to be against their use. No evidence currently exists which would indicate that back belts prevent injury, in fact, in one study those who wore back belts reported more back pain than workers who didn""t wear them. Workers wearing back belts may experience a false sense of security, causing them to lift unsafe loads. It has also been theorized that the prolonged use of back belts can weaken the muscles of the lower back, leading to a higher risk of injury when they are not worn. Additionally, back belts do not prevent forward bending, which again may be the most significant risk factor for lower back injury. NIOSH has determined not to recommend the use of back belts to prevent injury, and does not consider back belts to be personal protective equipment. Several US patents exist on various back belts including U.S. Pat. No. 4,709,692 to Kirschenberg (1987), U.S. Pat. No. 4,348,774 to Woodson (1982), and U.S. Pat. No. 3,603,316 to Lehman (1971). Despite all of the evidence suggesting that they do not prevent back injury, many companies still require their employees to wear back belts.
Another group of back safety devices provide an external force to assist the lower back muscles when lifting or bending. These devices can vary greatly in design and appearance, but typically employ a spring or elastic material to provide this force. Several of these devices are described in U.S. Pat. No. 6,129,691 to Ruppert (2000), U.S. Pat. No. 5,860,944 to Hoffman (1999), U.S. Pat. No. 5,951,591 to Roberts (1999), U.S. Pat. No. 5,816,251 to Glisan (1998), U.S. Pat. No. 4,829,989 to Deamer (1989), U.S. Pat. No. 3,570,011 to Naig (1971), U.S. Pat. No. 2,906,260 to Myers (1959), U.S. Pat. No. 1,812,529 to Haulbrook (1931), U.S. Pat. No. 1,746,067 to Zwalley (1930), U.S. Pat. No. 1,641,027 to Feaster (1927), U.S. Pat. No. 1,634,621 to Martinez (1927), U.S. Pat. No. 1,544,162 to Vigne (1925), U.S. Pat. No. 1,553,874 to Nivens (1925), U.S. Pat. No. 1,371,690 to Kelly (1921), U.S. Pat. No. 1,384,299 to Brown (1921), U.S. Pat. No. 1,202,851 to Kelly (1916), U.S. Pat. No. 903,403 to Quick (1908), U.S. Pat. No. 836,802 to Daniel (1906), U.S. Pat. No. 703,477 to Russell (1902), U.S. Pat. No. 654,173 to Mendenhall (1900), U.S. Pat. No. 637,156 to Potts (1899) and U.S. Pat. No. 443,113 to Ray (1890). Although these devices take some of the load off of the lower back muscles, they do not prevent the forward bending motion, and accordingly, have not provided a satisfactory solution to lower back injuries caused by bending and lifting activities.
A variety of other unique back safety devices have been developed over the years, and are often referred to simply as back braces. These devices often include features similar to the back belts described above, but have additional straps usually attached to the thighs or shoulders, and often have rigid components that restrict certain motion. Some of these devices are described in U.S. Pat. No. 5,172,703 to Tiede (1992), U.S. Pat. No. 5,040,524 to Votel (1991), U.S. Pat. No. 3,521,623 to Nichols (1970), U.S. Pat. No. 3,029,810 to Martin (1962), U.S. Pat. No. 1,316,915 to Meyer (1919), U.S. Pat. No. 1,098,492 to Gibson (1914), U.S. Pat. No. 781,544 to McMurtry (1905), and U.S. Pat. No. 401,223 to Smith (1889). Some of these devices do somewhat restrict forward bending, such as U.S. Pat. No. 1,008,500 to Thornton (1911) and U.S. Pat. No. 1,191,769 to Curts (1916), however, as the forward bending motion is restricted with these devices, the ability of the wearer to bend properly using the squat bending method is also completely restricted. A recent U.S. Pat. No. 5,259,833 to Barnett (1993), describes a back brace designed to prevent forward bending. The back bending motion limiting apparatus described in this patent consists of a pair of shoulder straps connected to the wearer""s pants. When these straps are tightened, they prevent the forward bending motion. Although this device can prevent forward bending, it also prevents the wearer from squat bending. None of the prior art described above can both prevent forward bending, and at the same time allow squat bending.
The invention uses a back strap connected to a pair of shoulder straps which limit the forward bending movement of a user in combination with leg straps attached to the back strap through a ring at the base of the back strap and the user""s feet. The length of the combined leg straps, back strap and shoulder straps is adjustable to limit the degree of bending of the wearer while standing erect to a small angle of forward bending and limit the forward bending to a larger degree while squatting since there will be some slack created in the length of the combined restraint when in the squatting position. The length of the belt thereby prevents back injuries by limiting the forward bending of the wearer while standing erect, which is an improper position for heavy lifting by bending the back, while allowing bending of the back while in a squatting position for lifting objects while using the leg muscles which is the proper way to lift heavy objects, thus preventing injuries to the wearer.
Accordingly, several objects and advantages of the present invention are:
(a) To provide a back safety harness which will prevent the wearer from forward bending past a predetermined angle without restricting the wearer from squat bending (i.e. straight back, bent knees).
(b) To provide a back safety harness which, while preventing forward bending, does not restrict the wearer""s ability to walk naturally or perform other normal activities such as sitting or climbing/descending stairs.
(c) To provide a back safety harness, which while preventing forward bending, does not interfere or restrict activities performed by the wearers shoulders, arms, and hands.
Furthermore, this safety harness is easy and convenient to use, small, light-weight, comfortable, durable, and can be easily and quickly adjusted to fit most any body type. Additionally, this device is made from very low cost, common components. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.